An internal combustion engine is used as a power source in various usages. For instance, as a power source for running a power generation plant or the like, a gas engine is known, which is high power and which uses an economically efficient gas such as methane gas.
Meanwhile, when air or air-fuel mixture is supplied to a combustion chamber of each cylinder in an internal combustion engine, an air-supply valve (scavenging port) disposed on the cylinder opens to let the gas through into the cylinder. At this time, the amount of air or air-fuel mixture supplied to the cylinder is determined depending on the differential pressure between the cylinder and an air-supply manifold. At this time, the differential pressure between the cylinder and the air-supply manifold generates a negative pressure wave, which causes air-supply pulsation corresponding to the combustion cycle. Further, due to the air-supply pulsation, the differential pressure between the cylinder and the air-supply manifold changes with time, and thus the amount of air supplied to each cylinder is affected by the differential pressure. In particular, when the differential pressure between the cylinder and the air-supply manifold decreases, the air-supply amount to the cylinder decreases, which may deteriorate the engine efficiency.
Patent Document 1 discloses a technique to suppress such deterioration of the engine efficiency. The document discloses providing an impulse valve in the intake pipe downstream of a throttle valve and controlling the opening valve of the impulse valve in synchronization with the opening degree change of the throttle valve, which makes it possible to obtain a good following performance even in a case where the air-supply amount changes with the operation state change of the engine, and to suppress deterioration of the engine performance.